A voltage-sourced conversion technology recently highlighted in high voltage direct-current (HVDC) transmission systems has a lot of advantages in the design of multi-terminal networks, compared to the conventional current source converters employed in the prior art.
As the voltage-sourced conversion technology advances, establishment of the HVDC multi-terminal network was facilitated, and a smart grid plan for a distributed renewable energy network was expedited. For this purpose, it is necessary to address technical problems in a DC circuit breaker for protecting transmission lines in advance.
Unlike the conventional DC circuit breakers, the voltage-sourced conversion technology requires low-loss and fast switching characteristics. Therefore, a hybrid circuit breaker was developed, in which mechanical conversion for satisfying a low-loss requirement and power-semiconductor-based electrical conversion for satisfying a fast switching requirement are combined.
As well known in the art, the fast switch is an electric power device adapted to switch between open and close positions in a high speed to cut off an abnormal current such as a short-circuit current or close a circuit rapidly.
Such a fast switch is operated in a very high speed, for example, within several milliseconds or several tens of milliseconds. As a result, it is possible to minimize an electric arc accident that may be generated during a circuit open/close operation and reduce damage to power devices such as a distributor panel by rapidly cutting off an abnormal current.
FIG. 1 is a cross-sectional view illustrating a fast switch of the prior art.
Referring to FIG. 1, a high-speed closing switch 100 has a first electrode 10 inside a casing 200 that forms external appearance and a second electrode 20 that faces the first electrode 10 over the first electrode 10. The first electrode 10 has an internal through-hole 14, and the second electrode 20 has a receiving recess 24 facing the through-hole 14.
The high-speed closing switch 100 further has a movable contact member 30 vertically movably housed inside the through-hole 14 of the first electrode 10. As the movable contact member 30 moves upward and is received by the receiving recess 24 of the second electrode 20, the outer circumferential surface of the movable contact member 30 adjoins with the inner circumferential surface of the through-hole 14, and the outer circumferential surface of the movable contact member 30 adjoins with the inner circumferential surface of the receiving recess 24. As a result, the first and second electrodes are electrically connected to each other.
In the prior art, a damping force is applied to a damping hole in order to absorb an impact on the contact when the operation is completed. However, in the prior art, since wear or damage is generated due to a mechanical motion, it is inevitable to perform maintenance disadvantageously.